Encoding: Flac header is not correct in stream mode

[RuralHunter]

I believe this problem also exists for other format.
In stream mode:
ffmpeg -i 'test.ape' -f flac - >test.flac
In file mode:
ffmpeg -i 'test.ape' -f flac test.flac

The output files of above 2 commands are different. The first one lacks the correct flac header. It is similar at least for wav output.
I just use this to transcode music files on the fly and found some players rely on the correct header to determine the stream duration and when to stop the playback.
It checked the encoding code and found the header is updated at the end of the encoding. This won't work in stream mode. I suggest write the header with correct values in the beginning though this might require an additional scan on the source file.

[Gyan]

The duration is updated by the encoder in extradata at the end of encoding, and it can't know where the end is, in advance, since filters may have been applied, the timestamps could have been scaled..etc. Output destination has to be seekable if you need this information stored.